Understanding regulation of hematopoiesis will lead to treatment of patients with bone marrow disorders, such as marrow failure or hemoglobinopathies. We plan to study such patients with clinical assessments and in vitro hematopoietic cultures, to correlate in vitro with in vivo findings. We hope to identify cytokines which increase hematopoiesis and Hb F, monitor marrow cytogenetics, investigate specific mutations, and evaluate the role of physiological oxygen tension.